Spiral conveyor systems employing an endless belt conveyor travelling around the periphery of a vertically mounted cage or drum have been commercially employed for heating or cooling various products. Such a system for fast freezing of food products, for example, is disclosed in U.S. Pat. No. 3,733,848, wherein the products are passed in a vertical helical path within an insulated housing and are contacted with cold CO.sub.2 gas blown generally tangentially across the conveyor flights.
Among the known spiral conveyor types that have been employed in such heating and/or cooling systems are those disclosed in U.S. Pat. No. 3,348,659 and other patents assigned to Ashworth Bros., Inc. One such commercial system widely known in the industry is the "Ashworth Lotension Spiralcage System", described in Ashworth Bulletin No. 071 (1970).